418 PALAEONTOLOGY OF NEW-YORK. 



Fig. 2 «. A cast taken from the impression of a dorsal valve in sandstone. 



Fig. 2y. An impression of the dorsal valve in sandstone. 



Fig. 3. A cast in sandstone of the ventral valve. The specimen has been weathered, and the 

 parts are not as salient as they 'otherwise would be. The hinge-line is obliterated 

 in the specimen. 



Other specimens of the casts, and the separate valves of the species, more recently obtained, 



have served to illustrate more -fully the characters here represented but imperfectly. 



Geological position and localities. In the Oriskany sandstone : Albany and Scho- 

 harie counties ( New-York), and Cumberland ( Maryland ). 



Clionetes cuiiiplanata. 



Plate XCIIL Fio. 1 a, b, c, d. 

 Chonttes eomplanaia : Hall, Regents' Report for 1858, p. 54; Pal»ozoic Fossils, 1857, p. 14. 



Shell transverse, longitudinally semielliptical, about two-thirds as long 

 as wide. Ventral valve flat or concave. Dorsal valve unknown : tubular 

 spines of the cardinal margin directed obliquely outwards. 



Surface marked by fine closely arranged bifurcating striae, which appear 

 to have been crenulated by closely arranged concentric striae. Some of 

 the specimens show distant imbricating concentric lines of growth : 

 interior striate - granulose ; muscular impression large, not strongly 

 marked. 



All the specimens seen of this rare species consist of internal and external casts 

 of the ventral valve, from which it is impossible to make out a complete description. 

 The few remaining impressions of the row of tubular spines along the cardinal 

 margin are Ijarely sufficient to show the presence of these appendages, and do not 

 clearly indicate their number, length, curvature, etc. It may be recognized by its 

 extreme ilatness, finely striated surface, a few distant laminae of growth, and great 

 proportional width. 



Fig. 1 a. An impression of the outside of the ventral valve of this species. 



Fig. 1 4. A similar impression in sandstone, showing the concentric lines of growth, 



Fig. 1 c. A cast of the interior of a ventral valve, showing the muscular impression and 

 cavities of the dental lamellae. 



Fig. 2 c ( in centre of plate, by error for Id). An enlargement of the imprint of the surface, 

 as sometimes seen in sandstone. 



Geological position and locality. In the Oriskany sandstone : Albany and Scho- 

 harie counties. ' 



